TNR (Trap, Neuter, Release) is the most effective way to deal with feral cats. Take a trapped cat in to a TNR facility and they'll give them shots, spay/neuter and cut off the tip of the left ear...The tipped ear is an internationally recognized indicator that the animal is fixed.
TNR lets the animals go about their business (after a shitty day or two) and keep living their best kitty lives, killing rodents and other pests (and unfortunately, the occasional bird) while keeping the population from completely ballooning out of control.
Years ago I built a jig that could be bolted onto a live animal trap. It had a solenoid to actuate the door of the trap, and a Bluetooth SOC where when an animal entered the trap, I'd get an alert on my phone and then could confirm what animal was in there and if it's the one I was trying to catch, actuate the door from the app. The idea was to keep from trapping a possum or trapping a cat that's already been fixed if there were multiple cats around. I think part of the reason it never went much further than my back yard and a few people in the local TNR community was that most TNR people are retirees volunteering their time, and they weren't super huge on new technology.